Colorado Gov. John Hickenlooper signs the state's gun-control bills into law Wednesday at the Capitol in Denver. / Ed Andrieski, AP

by Robin Webb, USA TODAY

by Robin Webb, USA TODAY

Colorado Gov. John Hickenlooper signed gun bills into law Wednesday that ban ammunition magazines holding more than 15 rounds and require background checks for firearm purchases made online or through private parties.

The laws, which take effect July 1, were signed by the Democratic governor the day after Tom Clements, executive director of the Colorado Department of Corrections, was gunned down in his home and on the eight-month anniversary of the mass shootings at an Aurora movie theater that left 12 people dead and nearly 60 wounded.

Colorado is now the first state outside the East Coast to strengthen its gun restrictions since last year's shootings in Aurora and Newtown, Conn.

Several relatives of the Aurora shooting victims attended the signing.

"You've given us a real gift today," said Sandy Phillips, mother of Jessica Ghawi, who died in the Aurora massacre. "Thank you so much. You're leading the entire country."

State Rep. Rhonda Fields, a Democrat representing Aurora, said the stricter regulations will keep guns "out of the hands of criminals, domestic violence offenders and the seriously mentally ill."

One provision of the bills states that anyone who legally owns a high-capacity magazine purchased prior to July 1 can maintain ownership without being in violation of the new state laws.

Magpul Industries, a major manufacturer of gun accessories in Denver, has said it would leave the state if the bills became law. The company employs about 200 Coloradans.

"It is disappointing to us that money and a social agenda from outside the state have apparently penetrated the American West," the company said in a statement on Monday.

Magpul's attorneys have cited the language in the bill as too broad, which, in their view, could allow for further infringement on gun rights.

In addition to a ban on magazines with a capacity of more than 15 rounds, the legislation also bans magazines "which hold fewer rounds, but are 'designed to be readily converted' to hold more."

According to Magpul's attorney Jonathan Anderson, "virtually every magazine on the market has an open floor plate, and that design makes every magazine readily convertible."

In a state where gun ownership is common, the new laws have sparked partisan ire.

"They have overreached, and there are going to be electoral consequences," said Republican state Sen. Greg Brophy.

Republicans have said criminals will still be able to obtain larger magazines in other states, and limiting magazine sizes will hurt the economy by eliminating jobs.

Some state law enforcement officials oppose the new background checks on legal grounds.

Weld County, Colo., Sheriff John Cooke told The Greeley Tribune this week that he "won't bother enforcing" the laws because it will be impossible for law enforcement to monitor and verify whether gun owners are in compliance.

Cooke said the laws are "feel-good, knee-jerk reactions that are unenforceable."